Converting to .25cal?

Converting to .25cal?

Joined: July 27th, 2007, 3:36 am

October 19th, 2010, 5:02 am #1

I have a 2240/60 project with a B&A 12Gr Bossvalve [Gas Hoggy!],RJ Breech,MellonAir .22 flow thru bolt and power adjuster.I want to get it off the backburner and convert from .22 to .25 cal using a 14-16" bbl.What can I expect velocity wise using C02 carts,this valve and the recommended port mod?
I plan on using a TOW or MountainAir bbl depending if he has one available in the length I want.

I know its tough to answer due to all the variables but any help will be appreciated.I've researched here and have found a bunch'o excellent info regarding PCP's but I'm not ready to make that investment yet,although I've quite a bit $$ involved in this build already.Unit will be mainly used for can/paper plinking and occassional rodent extermination.

Thanks!

Last edited by blkft1 on October 19th, 2010, 5:05 am, edited 1 time in total.
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Joined: June 2nd, 2009, 12:39 pm

October 19th, 2010, 2:59 pm #2

I built a .25 cal similar to what you describe with a 12" LW barrel. I got 525 fps average with Lasers, 12 shots per cart. I added a heavier spring but lost access to a chrony so I can't say how much fps it added.
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Joined: July 27th, 2007, 3:36 am

October 19th, 2010, 8:51 pm #3

With my current set up I'm getting around 17-20 full power shots before I can hear ny noticable difference.I dont have access to a Crony yet to see what velocity is though.I should have bought a debouncer for the RJ breech's when Big Ed was making them,I've heard they increase shot count.12 shots is not bad especially since I'm not shooting this everyday compared to my 392.May convert to PCP down the road.

Thanks Jack!
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Joined: March 31st, 2008, 8:31 pm

October 20th, 2010, 12:03 am #4

I have a 2240/60 project with a B&A 12Gr Bossvalve [Gas Hoggy!],RJ Breech,MellonAir .22 flow thru bolt and power adjuster.I want to get it off the backburner and convert from .22 to .25 cal using a 14-16" bbl.What can I expect velocity wise using C02 carts,this valve and the recommended port mod?
I plan on using a TOW or MountainAir bbl depending if he has one available in the length I want.

I know its tough to answer due to all the variables but any help will be appreciated.I've researched here and have found a bunch'o excellent info regarding PCP's but I'm not ready to make that investment yet,although I've quite a bit $$ involved in this build already.Unit will be mainly used for can/paper plinking and occassional rodent extermination.

Thanks!
Hi,

I converted a 2240 a couple years back and love the bigger caliber:
It was a Crosman Custom Shop 2300 base, which I added the MA .25 cal top end set (12" barrel & bolt w/extended probe), I used a CB Ultimate Breech and a B&A Boss Valve and am getting ~498fps.

There are a few more upgrades that really round it all out, but the MA barrel and B&A Boss valve seem to be a good match. I shoot allot of the 19.3 gram Webley Mosquitos through it with amazing accuracy for a hand gun.

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I also converted a 1377 to .25 cal a while back and love shoot that in the colder weather:
This conversion uses a MA .25 cal top end set (22" barrel & bolt w/extended probe) and RJ Long Breech Kit. I followed directions for the Modified "Hotrod" Valve and then finished it out with a few more mods. This one gets ~565fps with the mosquitos and is even more accurate than the modified 2240.

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Be careful, the .25 cal addiction is a hard one to get over.

Have fun,
Kevin

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Joined: July 27th, 2007, 3:36 am

October 20th, 2010, 7:18 pm #5

those guns look stunning!I guess I need to contact Roy about a 14" bbl.From my understanding they will fit the Crosman or similar breech like my RJ.I looked at the TOW .25cal ACP bbl but once I gather the tools or pay someone to mod it to work it will come out the same,plus Roys I gather are Lothar Walther and come choked?
I'm guessing it'll work with my .22cal Mellonair flow thru bolt with a larger size O-ring?Plus I wonder if there'll be any interference between the flow thru bolt which has no prob,pellet skirt and the bbl chamber?
Last edited by blkft1 on October 21st, 2010, 12:16 pm, edited 1 time in total.
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Joined: March 31st, 2008, 8:31 pm

October 20th, 2010, 8:48 pm #6

Hi Jack,

Roy will work with you with the LW barrels. Neither of mine are choked as he can cut that part off if you want. I sent both the CB and RJ breeches to him so he could fit the barrels for me. Both experiences were professional and enjoyable. I learn something new every time I work with Roy.

Have Fun,

Kevin
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